ColorMap Class Reference

Class to represent a color map. More...

#include <dune/fufem/functions/portablepixelmap.hh>

Public Types
enum	ColorMapFileFormat { CM }
enum	IODataFormat { ASCII , Bin }
typedef unsigned char	CType
typedef unsigned short int	KeyType
typedef Dune::FieldVector< CType, 3 >	Color
	The type used to represent the color.
typedef std::map< KeyType, Color >	ColorKey
	The actual type of the ColorKey.

Public Member Functions
	ColorMap ()
	ColorMap (const std::string filename)
	Construction from dune-fufem colormap (.cm) File.
bool	insertInColorKey (const KeyType key, const Color color)
	insert keyvalues into the ColorKey
Color	map (const double fMin, const double fMax, const double fVal) const
	maps a scalar to a color
double	inv_map (const double fMin, const double fMax, const Color color)
	maps a color to a scalar
void	exportColorMapGraphic (const std::string filename="colormap.ppm", IODataFormat df=Bin) const
	writes a ppm-file to harddisk as an illustration of the colormap
void	exportColorMap (std::string filename="colormap", ColorMapFileFormat format=CM)
	writes the colorkey to a file in an own format (.cm)
int	size ()

Detailed Description

Class to represent a color map.

The ColorMap class represents a (not quite) invertible mapping \(\Gamma:\mathbb{R}\supset[a,b]\longrightarrow \text{RGB}\) where the interval boundaries \( a,b\) are not fixed for any instance of that class but rather have to be specified when the methods map() resp. inverse_map() are called. Internally the mapping is represented by the ColorKey which maps \(\gamma:\mathbb{N}\supset[0\ldots N]\supset D\longrightarrow\text{RGB}\). Return colors are linearly interpolated between the two adjacent keys in the ColorKey after the linear transformation \(\tau:[a,b]\ni r\mapsto\xi\in[0,N]\subset\mathbb{R}\).

A ColorMap can be created from single keys that are interpolated or from files in either an dune-fufem native (.cm) format. This file formats may also be exported. Lastly a PPM-file representing the colormap can be exported, e.g. for illustrative purposes.

• Extract Color Type, make it a template (?) -> Allow for arbitrary number of color channels
• Make CType variable -> Allow for larger channel width
• unify PortablePixelMap, PortableGreyMap -> PortableArbitraryMap

Member Typedef Documentation

Color

typedef Dune::FieldVector<CType, 3> ColorMap::Color

The type used to represent the color.

Presently only three dimensional color spaces are supported. Each channel is expected to contain integer values between 0 and 255.

ColorKey

typedef std::map<KeyType, Color> ColorMap::ColorKey

The actual type of the ColorKey.

The ColorKey is expected to contain \(2\leqslant n\leqslant N+1\) entries where \(0<N<65535\). There are two ways to obtain a valid ColorKey. Firstly by calling insertInColorKey() at least twice with different keys after default constructing the ColorMap or secondly by calling ColorMap(const std::string filename) on a valid dune-fufem colormap (.cm).

Attention

It is assumed that there exists a key 0. This assumption is not enforced however!

CType

typedef unsigned char ColorMap::CType

KeyType

typedef unsigned short int ColorMap::KeyType

Member Enumeration Documentation

ColorMapFileFormat

enum ColorMap::ColorMapFileFormat

An enum for the employed file format to read/write colormaps

Enumerator
CM

IODataFormat

enum ColorMap::IODataFormat

An enum for the data format of exported grafix files

Enumerator
ASCII
Bin

Constructor & Destructor Documentation

ColorMap() [1/2]

ColorMap::ColorMap ( )

inline

The default constructor

ColorMap() [2/2]

ColorMap::ColorMap ( const std::string  filename )

inline

Construction from dune-fufem colormap (.cm) File.

Constructor that builds up the ColorKey from a dune-fufem colormap file (.cm).

Parameters

filename

The path of the Colormap file

Member Function Documentation

exportColorMap()

void ColorMap::exportColorMap ( std::string  filename = "colormap", ColorMapFileFormat  format = CM  )

inline

writes the colorkey to a file in an own format (.cm)

This method writes a file to disk which may be used to construct a ColorMap and appends an extension to filename (.cm) if none is given.

Parameters

filename	The path the output file shall be written to
format	The file formmat to use

exportColorMapGraphic()

void ColorMap::exportColorMapGraphic ( const std::string  filename = "colormap.ppm", IODataFormat  df = Bin  ) const

inline

writes a ppm-file to harddisk as an illustration of the colormap

This method writes a graphics file in ppm format (256x25 pixels) to harddisk illustrating the colormap.

Parameters

filename	the path the output file shall be written to
df	The IODataFormat to use

insertInColorKey()

bool ColorMap::insertInColorKey ( const KeyType  key, const Color  color  )

inline

insert keyvalues into the ColorKey

Parameters

key	the integer (in [0,65535]) mapped to color
color	the color key is mapped to

Returns

true when insertion successful, false otherwise

inv_map()

double ColorMap::inv_map ( const double  fMin, const double  fMax, const Color  color  )

inline

maps a color to a scalar

The method first fills in the ColorKey and then finds the key color closest to the argument in the sense of the one-norm (called keycol resp col in the following). The return value is interpolated between keycol and the next closest color to col among the predecessor and the successor of keycolor (called adj for adjacent) in the following (crude) way:

\[ \text{returnval} = \tau^{-1}\left((1-\lambda)\cdot\gamma^{-1}(keycol) + \lambda\cdot\gamma^{-1}(adj)\right)\qquad\text{, where }\lambda=\frac{\lVert col - keycol\rVert_1}{\lVert col - keycol\rVert_1+\lVert col - adj\rVert_1} \]

(for notation \(\tau, \gamma\) see above)

Warning

In order to be of any real use color is not restricted to values in the filled in ColorKey. This, however, leads to possibly highly inaccurate if not meaningless results, if color is too "far away" of the colors in the ColorKey. Also

x==inv_map(fMin,fMax,map(fMin,fMax,x)) 

will probably evaluate as false. So inv_map() is ONLY a hopefully APPROXIMATE inverse of map().

Parameters

fMin	lower interval boundary for values represented by the colormap
fMax	upper interval boundary for values represented by the colormap
color	a color (best included in the ColorKey) to be inversely mapped to a scalar in [fMin,fMax]

Returns

the scalar mapped to

map()

Color ColorMap::map ( const double  fMin, const double  fMax, const double  fVal  ) const

inline

maps a scalar to a color

Parameters

fMin	lower interval boundary for values represented by the colormap
fMax	upper interval boundary for values represented by the colormap
fVal	scalar in [fMin,fMax] to be mapped to a color

Returns

the color mapped to

size()

int ColorMap::size ( )

inline

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The documentation for this class was generated from the following file:

• portablepixelmap.hh